The present invention relates to a display device, and particularly to a display device which seals a display area formed in at least one of two substrates such that the display area is shielded from an ambient atmosphere, and which thereby avoids deterioration of pixel-forming components of the display area, and achieves a long lifetime.
With an arrival of an advanced information society in recent years, a demand for a personal computer, a car navigation system, a portable information terminal, information and telecommunications equipment or a combination thereof is increasing. For a displaying means for these products, a thin, light-weight, low-power display device is suitable, and a liquid crystal display device, or a display device employing a light-emitting type optoelectronic element such as an electroluminescent element or LEDs is used.
The display device employing the light-emitting type optoelectronic element has good readability, wide viewing angles, and is suitable for displaying of moving images because of its fast response, and therefore it is suitable particularly for a video display.
In particular, a display device employing an organic electroluminescent element (also referred to as an organic LED element, hereinafter sometimes abbreviated as an OLED) using recent organic light-emitting material is highly expected for practical use with the rapid improvement of luminous efficacy together with the development of network technology enabling video communication. The OLED has a diode structure having an organic light-emitting layer sandwiched between two electrodes. In general, thin film transistors (hereinafter referred to as TFTs also) are used as switching elements for selecting of pixels in the OLED display device employing the above-explained OLED element.
A display device including, in addition to the above-described organic EL element, a liquid crystal display device or the like, for example, is generally called a panel-type display device, uses a substrate made preferably of glass as its display screen, and is provided with an image-displaying structure on its inner surface. The rear surface of the substrate is covered with a can (a sealing can) made of glass or metal, and the peripheries of the substrate and the can are sealed together to block gases such as humidity and oxygen of the ambient atmosphere from entering the display device, and thereby to avoid deterioration in characteristics of the image-displaying structure due to humidity,
In particular, in the display device employing the organic EL element, it is necessary to block gases such as humidity and oxygen of the ambient atmosphere from entering the display device, and to eliminate gases evolving from various thin film materials which are components of the image-displaying structure included in the display area. To this end, it is necessary to have a structure which seals the display-screen-side substrate and the rear substrate together along their peripheries hermetically to block moisture from entering the sealed envelope and thereby keep the sealed space dry, and adsorbs gases evolving within the sealed space.
The prior art of this kind for keeping the space sealed between the substrates dry is known as disclosed, for example, in Japanese Patent Laid-Open No. Hei 9-148066 laid open on Jun. 6, 1997. In this Publication, a desiccating agent is inserted between a display-screen side glass substrate and a rear substrate (a sealing can). However, a structure sealing the display-screen side glass substrate and the rear substrate is not taken into consideration, and since there is a limit in the moisture absorption capability, it is difficult to continue adsorbing the moisture entering via the sealing structure of both the substrates for a long period of time.
An arrangement is disclosed in Japanese Patent No. 2845239 issued on Jan. 13, 1999 and others, in which adhesives differing in curing conditions depending upon wavelengths and intensities of ultraviolet rays irradiated onto the adhesives are laminated in two (or three) layers, but the influences on elements within the display area such as a display pixel or a liquid crystal material by the adhesives are not taken into consideration. Further, the technology relating to the liquid crystal display device is disclosed in Japanese Patent Laid-Open No. Hei 2-73229 laid open on Mar. 13, 1990 and others, in which an ultraviolet curable sealing material is provided internally of a thermosetting seal, but in this case, either, the influences on the elements within the display area are not taken into consideration.
It is an object of the present invention to provide, paying attention to a fixing structure (a sealing structure) of the display-screen side substrate and the rear substrate, a display device which blocks moisture and gases entering the sealed space via facing portions of peripheries of the two substrates, and reduces deterioration in characteristics caused by gases evolving within the space sealed between the two substrates to obtain a good image display for a long period of time. For simplification of explanation, an explanation will be made hereinafter in which a display-screen-side substrate provided with an image-displaying structure is referred to as a first substrate, and the rear substrate is referred to as a second substrate.
To achieve the aforementioned object, according to the present invention, the first and second substrates are sealed together by disposing an adhesive layer (or an adhesive film) composed chiefly of a material derived from a sol-gel solution between the inner surfaces of the peripheries of the first and second substrates such that the adhesive layer surrounds the image-displaying structure. Further, according to the present invention, along with the adhesive layer composed chiefly of a material derived from a sol-gel solution, a rubber layer having good affinity to the first and second substrates is sandwiched between the first and second substrates such that the rubber layer surrounds the display area.
The above-mentioned first and second substrates are firmly bonded together by the so-called so-gel reaction of a sol-gel solution of ethoxy silane alone or a solution containing alkoxide of metals such as Zr, Ti, Sn or the like, which is interposed between the two substrates. As a rubber (a rubber layer, or a rubber member), a rubber member such as silicone rubber having good elasticity and a good affinity to the substrates is used. In a case where one of the surfaces to be fixed is metal, adhesion is improved by mixing metal particles as fillers with the rubber member. Further, when a rubber member having a good affinity to the substrates is inserted between the two substrates, intimate contact between the two substrates can be obtained with a relatively low pressure applied. When a light-blocking substance such as carbon is mixed into the rubber layer, the light-blocking substances reduces influences on the elements within the display area caused at the time of curing of a photocurable adhesive, or caused by unnecessary light from the outside via the sides or the back.
Further, a known adhesive such as an acrylic system resin or an epoxy system resin may be used as an adhesive, in place of the adhesive layer derived from the sol-gel solution, or together with the adhesive layer derived from the sol-gel solution, in combination with the rubber layer. When the adhesive layer derived from the sol-gel solution or the known adhesives are used, a dehumidifying agent or a free-oxygen absorber or both of them are kneaded to the material of the rubber layer to thereby enable keeping the space between the two substrates in a dried condition. It is noted that the dehumidifying agent or the free-oxygen absorber may be provided between the substrates separately from the rubber.
The typical structures of the present invention will be described as follows:
In accordance with an embodiment of the present invention, there is provided a display device comprising: a first substrate; a second substrate disposed to face said first substrate; a plurality of pixels disposed in a display area on an inner surface of said first substrate; a rubber member disposed between said first and second substrates to surround said display area, and sealing said display area from an ambient atmosphere; and an adhesive layer sealing together said first and second substrates along peripheries thereof, wherein said adhesive layer is derived from a sol-gel solution.
In accordance with another embodiment of the present invention, there is provided a display device comprising: a first substrate; a second substrate disposed to face said first substrate; a plurality of pixels disposed in a display area on an inner surface of said first substrate; a rubber member disposed between said first and second substrates to surround said display area, and sealing said display area from an ambient atmosphere; and an adhesive layer sealing together said first and second substrates along peripheries thereof, wherein said adhesive layer is made of one of a photocurable adhesive and a thermosetting adhesive.
In accordance with another embodiment of the present invention, there is provided a display device comprising: a first substrate; a second substrate disposed to face said first substrate; a plurality of pixels made of an organic light-emitting material and disposed in a display area on an inner surface of said first substrate; a rubber member disposed between said first and second substrates, and having a first part surrounding said display area and a second part superposed on at least a portion of an area on an inner surface of said second substrate, said area directly facing said display area of said first substrate; and an adhesive layer sealing together said first and second substrates along peripheries thereof, wherein said rubber member seals said display area from an ambient atmosphere, and said adhesive layer is derived from a sol-gel solution.
In accordance with another embodiment of the present invention, there is provided a display device comprising: a first substrate; a second substrate disposed to face said first substrate; a plurality of pixels made of an organic light-emitting material and disposed in a display area on an inner surface of said first substrate; a rubber member disposed between said first and second substrates, and having a first part surrounding said display area and a second part superposed on at least a portion of an area on an inner surface of said second substrate, said area directly facing said display area of said first substrate; and an adhesive layer sealing together said first and second substrates along peripheries thereof, wherein said rubber member seals said display area from an ambient atmosphere, and said adhesive layer is made of one of a photocurable adhesive and a thermosetting adhesive.
In accordance with another embodiment of the present invention, there is provided a display device comprising: a first substrate; a second substrate disposed to face said first substrate; a plurality of pixels made of an organic light-emitting material and disposed in a display area on an inner surface of said first substrate; a rubber member disposed between said first and second substrates to surround said display area, and sealing said display area from an ambient atmosphere; and an adhesive layer sealing together said first and second substrates along peripheries thereof, wherein said adhesive layer is derived from a sol-gel solution, and a width of said adhesive layer is in a range of from 1xc3x97103 to 1xc3x97104 times a thickness of said adhesive layer.
In accordance with another embodiment of the present invention, there is provided a display device comprising: a first substrate; a second substrate disposed to face said first substrate; a plurality of pixels made of an organic light-emitting material and disposed in a display area on an inner surface of said first substrate; and an adhesive layer sealing together said first and second substrates along peripheries thereof from an ambient atmosphere, wherein said adhesive layer is derived from a sol-gel solution, and a width of said adhesive layer is in a range of from 1xc3x97103 to 1xc3x97104 times a thickness of said adhesive layer.
By the provision of the above-described structures, it is possible to provide a display device which blocks moisture and gases entering the sealed space via facing portions of peripheries between the first and second substrates, reduces deterioration in characteristics caused by gases evolving within the space sealed between the two substrates, improves the strength, and enables to provide a good image display for a long period of time, leading to high reliability and a long lifetime.
The present invention is not limited to the above-described structures and the structures of the embodiments described later, but needless to say, various changes can be made without departing from the technical idea of the present invention. Other objects and structures of the present invention will become apparent from the description of the embodiments described later.